I've recently been hacking on adding cpu_debug support for VIA CPU's to the Linux kernel. The code has today been published in the via-cpudebug branch of my linux-2.6-via git tree, the relevant commit is available here as commitdiff.
cpu_debug allows you to read all existing MSR (machine specific registers) from userspace using a debugfs interface.
Let's hope this code will - among other things - help us to debug any power / thermal management related issuses. I'm now going to be working on a small perl script that can interpret the power/thermal management related MSR values into something human-readable.